Interpretive Summary: In the US, animal agriculture accounts for approximately $100 billion annually, or half of all farm sales. The manure produced by dairy and beef cattle, poultry and swine contains vast amounts of nitrogen and phosphorus that in some regions can be land applied at agronomic rates on farms where it is produced. Manure provides essential and secondary nutrients for crop production, increases soil organic matter levels, and enhances soil physical properties and overall soil quality. Manure also contains energy that can be converted into fuel. This paper addresses potential agronomic benefits and pollution hazards associated with land-application of manure, followed by a brief discussion of the increasing attractiveness of using manure as fertilizer and energy in the current era of high energy costs.

Technical Abstract:
Manure benefits crop production through its fertilizer value and enhancement of soil physical properties and overall soil quality. The fertilizer N value of manure depends on the conservation of urine N. Approximately 25-35% of the N contained in manure of ruminant livestock (beef and dairy cattle, sheep) is available to the plant the season following application vs 50-60% for poultry and swine. As livestock and crop production become more specialized, it becomes more difficult to conserve manure nutrients and recycle them through crops. Manure N losses via ammonia volatilization, nitrate leaching and denitrification, and manure P losses in runoff are the principal pollution concerns. The economics of practices that enhance manure's fertilizer value, and capture of methane during manure storage may become increasingly attractive in the current era of high energy costs.